In July 1994 the Federation of American Societies for Experimental Biology (FASEB) will convene an international conference on Protein Phosphatases at Copper Mountain, Colorado. This will be the third such conference, and it has been authorized by FASEB because of the success of the 1990 and 1992 conferences. This application seeks partial support for the operation of this conference. Research on protein phosphatases is proceeding at a brisk pace, revealing the fundamental importance and unexpected complexity of these enzymes in the signal transduction pathways that govern cell growth and physiology. Within the past year dozens of new phosphatases and phosphatase regulatory subunits have been cloned. Now there is appreciation that protein phosphatases initiate important intracellular events such as T cell activation and G2 to M progression. Protein phosphatases offer vast potential for development of new and specific pharmacologic agents. Particular phosphatases already have been identified as the targets for the immunosuppressant drugs cyclosporin A and the target for tumor promoter compounds such as okadaic acid and calyculin A. Proteins encoded by DNA tumor viruses also target phosphatases inside cells and form stable complexes to transform cells. Like other FASEB summer conferences this meeting will select about 150 participants from applications, including representatives from industry and academia, including senior scientists, postdocs, and graduate students. There is a constant infusion of new researchers into this area and the 1994 conference will be important for a focused, yet comprehensive, introduction to the genetics, biochemistry, and cell biology of protein phosphatases. The Conference will consist of eight sessions, each with a discussion leader and four speakers who will be selected from investigators that have made important recent contributions. In addition two poster sessions will be organized, with published abstracts. At the last Conference more than eighty posters were presented for two days each providing an important format for scientific exchanges. Inclusion of women, minorities, and students as speakers and participants is a special priority. The 1994 summer conference on Protein Phosphatases will orient researchers, disseminate information and identify areas for new investigations.